(1) Field of the Invention
This invention concerns cable systems useful for improving the windload resistance of overhead doors.
(2) Description of the Art
Overhead doors are widely employed as garage closures because they achieve the desired result with minimal loss of floor space. It is desired to construct such doors from relatively lightweight materials such as fiberglass and sheet metal panels to reduce the difficulty involved in raising and lowering the door. However, even relatively light weight doors can weigh in excess of three hundred pounds.
A particular problem with large area doors arises in geographic areas such as so-called “hurricane zones” which are subject to high wind conditions. The wind load on a double width garage door can cause the door to flex inwardly with positive pressure and outwardly with negative pressure at the center and sufficient flexing can cause buckling, permanent deformation and, at the extreme, catastrophic failure.
Various methods have been proposed to address the need for reinforcement in sectional garage and warehouse doors. Some of the methods must be manually engaged to protect overhead doors during high wind events. A manually engaged apparatuses is disclosed, for example, in U.S. Pat. No. 6,385,916 in which a vertical bar associated with the door header must be manually engaged with a floor aperture in order to support the door during high wind events. The problem with manual systems are that they require human intervention. The system will not work if it is not activated.
This problem has been partly solved by integrating stiffening devices into overhead door panels. U.S. Pat. No. 6,161,606 for example adds one or more reinforcing struts along the length of overhead door panels. Another method disclosed in U.S. Pat. No. 6,473,988 uses one or more flexible members to transfer wind imparted forces to the guide rollers. Lateral reinforcing beams are also used in U.S. Pat. No. 6,408,926 to give overhead doors additional wind resistance. These solutions are also less than ideal because they require door manufactures to either retrofit doors on site to add the appropriate strengthening feature or to supply and support several different garage door panel designs. There is a need, therefore, for a system that solves one or more of these problems with current wind resistant overhead door systems.